Facile synthesis of both enantiomers of (pyrrolidin-2-yl)phosphonate from l-proline

Diastereoselective introduction of phosphono groups into l-proline derivatives at the 5-position was achieved with suitable selection of N-protecting group. N-Benzoyl-l-prolinate preferentially gave trans-phosphorylated products, which could be easily transformed into (S)-(pyrrolidin-2-yl)phosphonates. On the other hand, N-benzyloxycarbonyl-l-prolinate reacted with phosphite to give cis-substituted products, which could be easily transformed into (R)-(pyrrolidin-2-yl)phosphonates.